We measure the temperature dependent resistance of a niobium nitride(NbN) from room temperature to 4 K. The increasing resistance withdecreasing temperature can be explained by tunneling of electronsbetween grain boundaries. Once the detector is in the superconductingregime single photon counts can be registered. We find an optimal settingof the trigger level of 0.2 V to register detection events while minimizingthe influence of amplifier noise. From the measured voltage pulses weestimate a kinetic inductance of 200 nH for our devices. We explore theregime of high photon energies by plotting the count rate vs opticalpower on a double logarithmic scale. For photons with 500 nmwavelength the highest initial slope is equal to 2.6, indicating thatdetector tomography with 3 photon events realistic. Unfortunately,higher slopes are not observed and makes looking into detection eventswith more than 10 eV total energy difficult if not impossible.
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